Normal human infants perform a wide variety of rhythmical and stereotyped movements which are similar in form to those seen in patients with serious intellectual or emotional impairments. Previous research has suggested that these stereotypies in normal infants, like those ethologists study in other species, may be manifestations of intrinsic neural pattern generation. The patterned behavior seen in infants may be characteristic of maturing neuromuscular pathways under incomplete cortical control. The purpose of the proposed research is to measure the actual degree of variability in form and temporal patterning of rhythmical kicking, a common stereotypy in normal infants, and to test the hypothesis that these movements become more stereotyped both as the behavior becomes more mature and as the infant's arousal increases. To do this, I will record rhythmical kicking by videotape in normal infants at three ages and under two arousal conditions. The tapes will be analyzed frame-by-frame to measure the variability in the duration of the movements and in the vertical displacement of the leg. These data will provide a behavioral measure of the comparative rigidity of patterned behaviors in humans as a function of available neural processing capacity as measured by age and arousal level. Stereotypy in normal infants can then be compared to similar measurements available for other species, and with future research, to stereotypies in abnormal human populations.